1. Field of the Invention
This invention relates to a novel liquid crystal compound having an optically active group and a liquid crystal composition containing the same. More particularly it relates to an optically active phenylpyrimidine compound useful as a component of ferroelectric liquid crystal compositions and a ferroelectric liquid crystal composition containing the compound.
2. Description of the Related Art
At present, TN (Twisted Nematic) display mode has been most broadly employed. This TN liquid crystal display has a number of advantages such as low driving voltage, small power consumption, etc., but it is inferior in the aspect of response rate to emissive mode display elments such as cathode rays tube display, electroluminescence display, plasma display, etc. A new TN mode display element having a twist angle enlarged to 180.degree.-270.degree. has also been developed, but it is also inferior in the aspect of response rate. Various efforts for improvement have been made, but a liquid crystal element having a high response rate has not been realized. However, in the case of a new display mode using ferroelectric liquid crystals, which mode has recently been extensively researched, there is a possibility of notably improving the response rate (Clark et al, Applied, Phys. Lett., 36, 899 (1980)). This display mode is directed to a method utilizing chiral smectic phases such as chiral smectic C phase (hereinafter abbreviated to SC*). Phases exhibiting ferroelectric properties are not limited only to SC* phase, but it is known that chiral smectic F, G, H, I and the like phases exhibit ferroelectric properties. When these ferroelectric liquid crystals are utilized for display elements, liquid crystal materials exhibiting ferroelectric liquid crystal phases in a broad temperature range including room temperature have been desired. At present, however, no single compound which satisfies such a requirement has been known; hence liquid crystal compositions obtained by combining some compounds to thereby satisfy the required specific feature as much as possible have been used.